include: env: ti: mmc: envboot/mmcboot: Check result of mmc dev before proceeding

If mmc dev reports that the device is not present, there is no point in
proceeding further to attempt to load the files.

Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
1 file changed